20mph Speed limits do not work

They have been tried in a number of Locations around the UK and none have resulted in reduced speeds or safer roads. What are the reasons 20mph limits do not work and what did Brighton & Hove find attractive in a scheme which has failed everywhere else?

On Monday 8th April, Brighton & Hove became the latest city to introduce a signs only 20 mph speed limit covering most of the city centre. The new limit, without enforcement, has made no difference to the speed of traffic and the stated aims of improving the environment and making the city a safer place look likely to fail.

At first sight the scheme is big, bold and a bargain at £1.5 million. On examination, all we see is a few 20mph signs mounted on lamp posts and a local authority indulging in some political posturing. I doubt this is what people had in mind when petitioning for action against speeding cars in their streets. The conventional alternative is to install targeted 20mph zones complete with traffic calming measures proven to work.

Brighton & Hove City Council find themselves reliant on the passive compliance of drivers, having chosen to disregard Department for Transport guidelines to impose 20 limits where the average vehicle speed is already below 24mph. They have ignored the views of the Association of Chief Police Officers who maintain a similar view that 20 limits should be self enforcing and the council has also failed to take into account that almost every driver regularly breaks speed limits and the reasons they have for doing so.

Intelligent Approach to Road Safety

Our experiences demonstrate that a more intelligent approach can influence driver behaviour and speeds can be controlled by understanding the way drivers make judgements through their perception of the road ahead.

One of the main reasons we exceed the speed limit is the knowledge we will probably get away with it. Often, people admit to simply following the car in front and not wanting to hold up the normal flow of traffic. It’s not really a reason but an excuse we find acceptable. If we want to control the speed of that ‘normal flow’, we must first deal with the core beliefs affecting our driving decisions.

In the context of speed, a good example of a core belief is where a driver knows he can see everything in his stopping distance and cannot possibly be involved in a collision with a pedestrian. This is not someone who will be influenced by claims of improved survival rates for pedestrians at 20mph?

“Rules are for the obedience of fools and the guidance of wise men”

The Douglas Bader quote may contain a hint of arrogance but it’s true to say that even relatively inexperienced drivers possess the ability to accurately judge speeds appropriate to the surroundings and if we want drivers to slow down a little more in certain places perhaps we should think about removing unrealistic speed limits and change the surroundings instead.

New Road in Brighton is an excellent example of Shared Space where there is no segregation of vehicles and pedestrians.

There is plenty of evidence that drivers respond to the subtlety of intelligent road design. Brighton has one road where the speed limit has been 20mph for years but street design alone is keeping the average vehicle speed down to a walking pace. It is a great shame that most car drivers mistakenly believe the road is pedestrian only and avoid the area.

Shared Space is clearly not practical for streets where there is a high volume of through traffic but there are other more suitable intelligent road design alternatives. A great example can be found in the London Borough of Kensington and Chelsea. The project was essentially a ‘make over’ for Kensington High Street which was started in January 2001 and took about two and a half years to complete.

Kensington High Street

The aim was to change the balance between cars and pedestrians and move it slightly towards the pedestrian by creating a greater ease of movement between the north and south footways without restricting vehicle capacity and minimising any restriction of flow. This was mainly achieved with additional and simplified pedestrian crossings and a small amount of pavement widening.

In a move reminiscent of ‘Shared Space’ the removal of pedestrian guard railings and a minimalist approach to signage including the combining of traffic signals with lamp posts creates an impression that pedestrians belong and have a right to be there. Other improvements including the introduction of high quality street furniture and new paving surfaces were not cheap but the result was a transformation of the environment and improved road safety with fewer accidents. Benefits of this kind don’t come cheap.

In Kensington High Street before the improvements, in the years between 1998 and 2000, there were 8 people killed or seriously injured and 62 suffering slight injuries. After the changes, between In September 2003 to August 2005, 4 were killed or seriously injured and 36 slight injuries.

43% Casualty Reduction

The decrease in casualties was an amazing 43% which remains impressive even when compared with a decrease across the capital of over 17% in the same periods. Whilst it is true that average vehicle speeds have reduced in Kensington High Street, the casualty reduction was achieved without imposing a 20mph limit.

Design that changes the character of a street can also change the perception of an appropriate speed in the minds of drivers. The point here for Brighton is that it doesn’t work the other way round. Simply changing the speed limit does not mean a change of character will follow automatically.

We expect our local authorities to seek out the best value for money and avoid wastage. It seems to me that when looking at ways of improving road safety and creating a better environment, scale and quality are vital considerations. Essentially, it comes down to a simple choice between small targeted schemes that work or large schemes that flop. I know which I prefer.